Ethanol can be produced from grain-based feedstocks, cellulosic feedstocks, and other plant material. In a conventional ethanol plant producing ethanol from corn, corn kernels are processed to separate the starch-containing material from other matter. The starch-containing material is then slurried with water and liquefied to facilitate saccharification and fermentation. The product of fermentation is beer, which comprises a liquid component including ethanol and water and a solids component including unfermented particulate matter.
According to a typical process used at conventional ethanol plants, the liquefaction of the starch-containing feedstock is done by ‘cooking’ the slurry at a temperature at or near the boiling point of water (e.g. in the range of 60-80 degrees C. or greater). According to an alternative process, developed and implemented by POET Research LLC, the assignee of the present application, and described for example in U.S. Patent Pub. No. 2005/0239181, raw starch may be converted and fermented without ‘cooking’ or liquefaction.
In a conventional ethanol plant, the fermentation beer product may undergo a distillation process to produce ethanol and stillage. The stillage, or wet solids, can be dried into distillers dried grains, an operation in which water is removed from the solids, typically in a gas-fired dryer.